I am in a stalemate moment for now. My current system on all three computers is OS X 10.11.
I have to be on this system in order to run all programs and plugins properly.

My concern is Finale. I have been using it for 18 years.

Right now it is either v2014.5 or v25.5. In both cases the speed on all my machines is extremely slow.
Inserting objects, dragging page or moving an object takes a very long time, or it is lagging extremely.
It is hard to work. I use large scores, or 'heavy' scores (above 60k items per score).

I am thinking to move to Sibelius 8.7 which I just upgraded to.

I feel that I will loose the full control that Finale offers to me, but the speed in Sibelius and magnetic positioning (not in all cases) is appealing to me.
I am also scared of entering into Sibelius and than realizing it is not as I expected it to work.

Any advice?
Thanks.

(Dorico I have never tried but I will check it in some years, some tools I am missing there.)

I'm sorry to hear that upgrading to Finale 25 hasn't remedied your speed issues. Aside from experimenting with alterations of your system to root out any problem sources, it's difficult to give good recommendations on how to proceed.

I would firstly contact MakeMusic to hear if they can shed som light on potential conflicts on both the software and hardware sides or offer any other sort of help.

Moving to Sibelius is certainly a viable option if all else fails. I did this a number of years ago, following some incredibly frustrating few months dealing with the disaster called Finale 2004. I then switched back when Finale 2007 was released.

You will indeed lose some flexibility with Sibelius, and certain parts of the interface will most probably be frustrating in the beginning, but it will surely be better than dealing with a constantly spinning beach ball or lagging interface.

I would probably start with an xml-file of one of your more challenging works, and testing the waters one important feature at a time to see if you can live with the results and the workflow.

Do you work with a "clean" template in Finale?
I used to work with a Finale template that grew from about 2006 to 2014. It got extremely slow over the years. For example in Fin2014 (or 2014.5?) opening the score manager took about 20 seconds. Then I redid the template from scratch. Took a few hours to re-setup everything, but in the end Finale was again very, very fast (e.g. the score manager doesn't take more than a second now).
But I am also working on a fast Windows computer (i7-3960x, 3.7 GHz with 32 GB).

I see. Once there was a test file on the forum.makemusic.com that was done from scratch in the current version. It ended up to be as slow as any other file. But I understand your point, that would be a clever procedure. The question is - if the default files inside of the setup procedure are done in that current version, or have been "upgraded" from the older versions continuously.

Dual boot to Win7 at the same machine shows no significant slowness. This justnconfirms that it is not a hardware issue, but the way Finale on Mac renders the output via the graphical card's drivers.

Stupid question, but running Finale on Windows is not an option for you?

And there is one thing one may not forget: Finale is single-threaded.
It means Finale doesn't take advantage of the new multi-processor developments from the last 10 years (as for example image or video processing software does), but only gets faster with higher CPU speeds (=GHz) or improvements of the CPU internals.
Probably it also depends a bit on the graphics chip, e.g. for Finale's redraw. But I assume that this doesn't influence the workflow so much.

If you run a benchmark test (like the free one from https://www.cpubenchmark.net/ ), you can probably judge Finale's performance from just looking at the single-threaded benchmark.

There is another interesting observation:
The plugin is about 15-25% slower (!), if Finale runs in standard fullscreen mode compared to minimized.
When Finale only has a very small window, it doesn't need much CPU/GPU power for redrawing during the plugin processing.

Oh, is it? I was assuming that they had changed that with the move to 64 bit in v25. Isn't 64 bit synonymous with multi-threaded? It seems I need to improve my general IT knowledge. Anyway, your hint about the single-threaded benchmark explains why Finale 25 still isn't exactly fast on my computer. Faster than 2014.5 and not remotely as bad as OCTO describes, but still... Thanks for the info, Jan!

In simple words 64bit only means that the memory blocks that the processor processes are 64bit wide and not 32bit, and that it can address larger memory sizes (so you can easily address more than 4 GB RAM in 64bit, but not in 32bit which is limited to 4GB). This by itself doesn't mean any speed boost for typical processing cases. It is only faster if the numbers that are processed are bigger than 32bit (which is usually not case)

Multi-threading means that several processes can be processed at the same time. So if you have 4 processes, a CPU that can process 4 threads at the same time is about 4 times faster than a single-threaded CPU. But it requires that you have tasks that can be divided into several equal subtasks. This is typically the case on image and video processing tasks, but more difficult in notation software. And it is even more difficult to make a old software multi-threaded.

Here is a screencam video that demonstrates the "minimized" screen behaviour above:
Finale's plugin performance is 23% better when it runs in minimized mode compared to full screen.https://www.youtube.com/watch?v=9l3F5ZfIIz4
In minimized mode the plugin takes 13,45 seconds, in full screen mode 16.65 seconds.

Thanks again, Jan, for taking the time to make this clear! Now that I read your explanation I seem to remember that I knew this once. Well, never mind. I can imagine that making old software multi-threaded is very difficult. This must be a change that goes deep into the basic architecture of the application.

It seems that you have both Finale and Sibelius. If you start doing new work in Sibelius, Finale will still be there. You're not going to try anything silly like converting all your old work into Sibelius, are you? What can we say except 'try it and see'?